This disclosure invention relates generally to transport refrigeration units and in particular to outer protective covers for transport refrigeration units of the type mounted to a wall of a mobile refrigerated cargo box.
Transport refrigeration units are employed for conditioning the atmosphere within the interior of a refrigerated cargo box, such as a refrigerated trailer of the type commonly pulled by a tractor cab. Commonly, the transport refrigeration unit is designed for mounting on the front wall of a trailer behind the tractor cab. A typical transport refrigeration unit includes a one piece, self-contained fully refrigerant charged, prewired, refrigerant/heating unit powered by an engine, commonly a diesel engine. The transport refrigeration unit further includes a condensing section and an evaporator section. In such a design, the evaporator section fits into a rectangular opening in the upper portion of the trailer front wall and therefore, when the transport refrigeration unit is installed on the trailer front wall, the evaporator section is located inside the cargo box of the trailer. The condensing section, which is located outside the cargo box on the front wall of the trailer when the transport refrigeration unit is installed on the trailer front wall, includes an engine-compressor drive package, condenser fan, condenser coil, radiator coil, control panel, relay module, refrigerant controls, piping, wiring and associated components.
A structural framework, formed of a plurality of structural frame members, supports all of the components and facilitates attaching the transport refrigeration unit to the trailer front wall. Also supported by the structural framework is an outer cover that includes the necessary air inlet and outlet openings for air flow through the condensing section, and a plurality of doors that may be opened to provide access to the interior of the transport refrigeration unit for maintenance and service.
The access doors may include both front and side doors which should be light in weight, having adequate structural strength so as to withstand significant impacts without being damaged structurally or cosmetically, and provide an attractive appearance. They should also have sufficient torsional stiffness to hold their shape and provide adequate sound damping capabilities. Generally a composite structure with a foam inner core has been used to obtain these characteristics. The use of foam adds complexity and expense to the manufacturing process.